This way, your KWallet is unlocked when you login. Note that your login and KWallet passwords must match, you must use Blowfish encryption for the wallet (not GPG), and the name of the wallet must be kdewallet (the default).

and enable the service with systemctl --user enable ssh-agent. Make sure you use WantedBy=basic.target and not WantedBy=default.target, as at least I had problems with ssh-agent not starting early enough with the latter.

Step 3: Install and configure ksshaskpass

pacman -S ksshaskpass

Then create /etc/profile.d/sshaskpass.sh with:

#!/bin/bash
export SSH_ASKPASS="/usr/bin/ksshaskpass"

This way, ksshaskpass, which will store your passphrase in your wallet, will be the preferred program to unlock your SSH keys.